How to calculate wire gauge (AWG) needed

To calculate the American Wire Gauge (AWG) size you need for a specific application, you’ll typically consider the maximum current the wire will carry and the maximum acceptable voltage drop.

Determine the maximum current: This is the maximum continuous current the wire will need to carry. You can find this information in the equipment specifications or by calculating it based on the power requirements of the device (P=IV, where P is power in watts, I is current in amps, and V is voltage).
Select the acceptable voltage drop: The acceptable voltage drop depends on the application. For most low-voltage applications, a voltage drop of 3% is often used as a guideline, but this can vary.
Calculate the wire size: Once you have the maximum current and the acceptable voltage drop, you can use the AWG wire size calculator. There are many online calculators available that can help you determine the appropriate AWG size based on these inputs.

Keep in mind that AWG sizes are inversely related to the wire diameter, meaning that a larger AWG number corresponds to a smaller diameter wire.

i need for 3.6v, 100mA and 4cm long?

For a project at work I was required to calculate __XX__XX__XX_x_xx_X-X_x__x

To determine the AWG wire size for my application, I need to consider the maximum acceptable voltage drop and the wire length. Assuming a maximum acceptable voltage drop of 3% and using the resistivity of copper (which is commonly used for wires), I can calculate the AWG size needed.

1) Calculate the resistance of the wire: The resistance of the wire can be calculated using the formula:

where $R$ is the resistance of the wire in ohms, $ρ$ is the resistivity of the wire material (copper has a resistivity of about $1.68 \times 1 0^{-8}$ ohm-meters), $L$ is the length of the wire in meters, and $A$ is the cross-sectional area of the wire in square meters.

The cross-sectional area can be calculated using the formula:

where d is the diameter of the wire in meters.

2) Calculate the voltage drop: The voltage drop across the wire can be calculated using Ohm’s Law:

where I is the current in amps and R is the resistance of the wire in ohms.

3) Check if the voltage drop is within the acceptable range: Calculate the percentage voltage drop using the formula

where $V_{source}$ is the source voltage (3.6V in your case).

4) Select the AWG size: Choose the AWG size that meets the voltage drop requirement. You may need to try different wire sizes to find the best match.

Let’s calculate this for a wire that is 4cm long.
To calculate the AWG wire size needed for your application, we’ll first convert the length of the wire from centimeters to meters (since the resistivity is typically given in ohm-meters). Then we’ll calculate the resistance of the wire and the voltage drop across it.

4.1. Convert wire length to meters:

4.2. Calculate the cross-sectional area of the wire:
The diameter of a wire is not directly provided in the AWG standard but can be calculated using the formula for the AWG wire gauge:

For AWG 36, $d \approx 0.005 mm$ , which is extremely small and impractical for most applications. This calculation suggests that I may need a smaller AWG wire size.

4.3. Calculate the resistance of the wire:
Using the formula where $ρ = 1.68 \times 1 0^{-8}$ ohm-meters for copper:

Since we don’t have the exact wire diameter, we can’t calculate the resistance accurately.

4.4. Calculate the voltage drop:

Using Ohm’s Law $V_{drop} = I \cdot R$ , where $I = 0.1$ A (100 mA):

$V_{drop} = 0.1 A \times R$

Again, we can’t calculate the voltage drop accurately without knowing the wire diameter.

Without knowing the exact diameter of the wire, I can’t determine the correct AWG size for my application. However, based on the calculations, you may need a much smaller AWG wire size than AWG 36 for a 3.6V, 100mA application over a 4cm length. I might consider starting with a larger AWG size, such as AWG 24, and then adjust based on actual measurements and testing.